It is known to fit mud flaps or splash guards behind the wheels of vehicles to protect the rest of the vehicle body from mud and debris that may be kicked up by the wheels. Conventionally, these mud flaps have been fitted to the interior surfaces of vehicle wheel wells. Recent mud flaps or splash guards usually are molded of a resilient polymer and are generally flexible. Little attempt has been made to provide a splash guard that will deflect around a predetermined hinge point, such as might happen if the lower edge of the mud flap encounters a rock or other upstanding obstacle. U.S. Pat. No. 8,651,528 to Earl discloses a wheel well-mounted splash guard in which a guard portion rotates around an axis when the guard portion hits a road obstacle. The axis is defined by intentional slots and gaps between neighboring walls of the molded splash guard.
Many light trucks and SUVs now come equipped with running boards, particularly where the passenger seats and foot wells are located at elevated positions. In the early 20th Century, automobiles often had running boards, a structural feature that fell out of favor in the decades following. It was known to attach splash guards and similar depending items from the running boards of these early vehicles. U.S. Pat. No. 1,805,933 to Victor discloses a tire guard which could be affixed to a vehicle running board in front of the rear wheel, so as to sweep debris out of the way of the tire. This device was attached to the running board by means of a helical spring. U.S. Pat. No. 1,809,711 to Kile discloses a semirigid splash guard affixed to the underside of a running board in such a way that its angle could be adjusted by the user. U.S. Pat. No. 2,059,869 to Holecek discloses a ground-effect antenna formed as a portion of a flexible flap suspended from a running board. Despite these early devices, no one has provided a mud flap, integrally molded of a polymer, having rigidifying three-dimensional structure in its flap such as convex curved surfaces, attachable to a running board rather than to a wheel well, and including a hinge permitting the mud flap to deflect over road obstacles.